viogpu_cmd_req
error = viogpu_cmd_req(sc, cmd, cmd_size, ret_size);
viogpu_cmd_req(sc, &tth, sizeof(tth),
static int viogpu_cmd_req(struct viogpu_softc *, void *, size_t, size_t);
viogpu_cmd_req(sc, &flush, sizeof(flush),